Adding a speed limiter on a DIY kit

[whitebalance]

Hi,
I have added a DIY kit on retro race bike. The bike works smooth and I am very happy.
But.... it's a 350W motor and it goes to fast and its therefore not legal.
It has pedal assist and I would like to add a speed limiter.

Can anyone point me in the direction to where I might find or how to change the speed limit?

The kit is this one: https://www.aliexpress.com/item/2014...043362109.html

Thanks for all help :)

Kristoffer

[max_volt]

May I ask what that graph represents.

[whitebalance]

hehe... that was a mistake. just some calculations I'm doing on a different topic :)

[HarryS]

The optional LCD display might have a speed limit setting, but if you have the 810 LED display, I do not think you can do anything simple.

[whitebalance]

Thanks for the input. So my chance is then to change the controller?

[MoneyPit]

Why not just add an extremely inexpensive wireless speedometer and monitor yourself? Maintain the ability to increase speed if desired. You used essentially a no-name kit so nobody is going to have straightforward advice for it most likely.

If you are worried about legality, the motor's rating stamped on the casing is meaningless to your final drive output power, which is what most EU regs as well as USA regs (actually all that I have seen) care about. Actuall final output wattage is determined by volts x amps = watts. So if we use your nominal 36v battery output (which is customary) and your peak controller output (quasi-customary):

36*18 = 648 watts.

uh oh. How about we use the continuous rating instead:

36*12=432

Still not even close. And guess what? It never will be. A 12a/18a controller is quite weak. Most EU factory ebikes are similarly 'over' the limit. Its because the 250w standard is a bit of a joke in terms of how much good it can do you. So nobody conforms to the 250w final-output standard. Bafang for instance with their 250w G0 series.... all they do is take a 350w motor and stamp 250 on the casing. The motors are internally identical. Likewise a 750w motor will put out nothing additional to a 250w motor. The motor's rating has nothing to do with its output.

[whitebalance]

If it was that simple it would be great. Unfortunately if I am involved in an accident without a Pedal Assist that shuts the motor of at 25km/hr, I will get the blame and a fine.

I agree with you wrt. output++, but the cut off at 25km/hr is independent from that. :(

[MoneyPit]

Well, the answer may be you can't get there from here. If the motor connections are not proprietary and you can use another controller from another vendor... maybe.

[Fred]

Could the OP not use a Cycle Analyst to limit speed and/or current? Probably more $$ than a new controller but the CA provides a lot of other benefits.

[MoneyPit]

That would be about as much money as he paid for the entire kit, ****battery included****. Its not the best kit. I would hesitate to throw good money after bad in that kind of volume.

[tklop]

If it was that simple it would be great. Unfortunately if I am involved in an accident without a Pedal Assist that shuts the motor of at 25km/hr, I will get the blame and a fine.

I agree with you wrt. output++, but the cut off at 25km/hr is independent from that. :(

I know it can be tough to get through to the vendors there sometimes, but I'd contact the motor's supplier, through AliExpress and see if they've any suggestions.

But I have to admit, I'm confused.

Shoot. Cute zippy little skinny-tire bike like that? Seems to me, an average healthy rider should be comfortably pedaling along on leg-power alone at a good 27-28 kilometers per hour--all day long--unassisted--on a bicycle like that one.

Thus, my confusion: If in Olso, you can only "legally" get assist up to 25KPH, I can understand the reasoning behind that. But I wonder: Why would you have bothered to put a motor into that particular frame?

Was your plan to just not pedal at all anymore--and then at the same time try to get used to riding more slowly than you're accustomed to?

Did you want the assist to help you speed "off the line" more quickly--and then your legs take over above 25?

Are you only interested in using the assist while climbing hills?

I'd assumed you didn't have medical reasons for wanting to add assist, because if so, I'd have expected you to have chosen a more ergonomic bicycle type for your project. Racing-bike geometry isn't typically the kindest choice for those suffering with various sorts of leg/hip/knee/back/neck/wrist/elbow/arm/shoulder issues. So, I'd assumed you're healthy, and fit. But all my assumptions could be wrong--heck, they often are.

Are you wanting to work hard as ever, and show us wimpy assist-needing-folks up--when you have your motor do the "ghost pedaling" back there--humming uselessly along at full-throttle--while you're exceed that little thing's legal maximum-assist speed capacity with your legs?

Or do you want to pedal your now-heavier-with-mostly-unused-motor-on-it bicycle around with your leg-power until you're exhausted, and then switch the motor on, for a slower--yet assisted--trip back home?

I'm trying to figure out why you'd voluntarily choose to put assist on a bike--when that assist can't (legally) even match the bike's normal operating speed.

And I just don't get it.

Yet it's also your project--and you sure don't have to explain yourself to me!

Best of luck to you, either way

Take care,

Tklop

[whitebalance]

Tklop... wow that was a... reply

to be honest it was just a fun project. I found the vintage bike in my backyard, I took it all apart. Grinded, brushed, painted, adjusted, tuned because its cool fixing things. :)
Then I decided to make a ebike, because Oslo is either up or downhills. Sometimes its just nice to cruise upwards and arrive away or home without breaking a sweat, you know. :)

It looks rad and I loved fixing it from a rusty piece of shit.

don’t be so grumpy. Life will be much better :) :) :)

[tklop]

Tklop... wow that was a... reply

to be honest it was just a fun project. I found the vintage bike in my backyard, I took it all apart. Grinded, brushed, painted, adjusted, tuned because its cool fixing things. :)
Then I decided to make a ebike, because Oslo is either up or downhills. Sometimes its just nice to cruise upwards and arrive away or home without breaking a sweat, you know. :)

It looks rad and I loved fixing it from a rusty piece of shit.

don’t be so grumpy. Life will be much better :) :) :)

Right on!

Well--it does look like a fun bike.

I'd have never guessed it had been in such rough shape from your photos--you've done a nice job restoring it!

The assist idea--being for hill-use--that was one thing I suspected. Makes sense.

I hope you can get it set up the way you need--for the legalities.

Here in The Netherlands, we've got multiple speed categories for e-bikes, requiring different things.

The ones anyone can use without any registration or a helmet, only will assist riders up to about 25 kilometers per hour. If you want a faster e-bike, you can have one--but then you're required to use a helmet, and register your bike.

I mention this, because if it turns out to be impossible to limit your top assist speed to 25 KPH, could you consider instead registering your bike into a higher-speed category (if that sort of thing exists in your area)? Even if it costs you a little money--you won't have to start all over again, or risk legal issues.

Anyways, best of luck--I hope it works out! (And I'll try to watch that grumpiness) ;-)

Take care,

Tklop

[HarryS]

It would cost me about $80USD to order a conrtoller/LCD from China that has a speed limiter setting. I have found the speed limiter works on KT controllers that use the LCD3 display. I have one bike set to 30 km/hour.

[MoneyPit]

I have bikes with those same controlers and displays and as such am familiar with them... the question is whether or not those controllers will fit onto your motor plug?